Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session A14: General Fluid Dynamics: General I |
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Chair: Nikolaos Malamataris, University of Houston Room: 155 D |
Sunday, November 24, 2024 8:00AM - 8:13AM |
A14.00001: OUTFLOW BOUNDARY CONDITIONS FOR TIME DEPENDENT, PERIODIC FLOWS Advaith Nair, Nikolaos A Malamataris The issue of outflow boundary conditions arises in numerical experiments. In most cases, it is well known what kind of boundary conditions to impose at the inlet or along the sides of the domain. However, the outflow is almost always unknown as far as boundary consitions is concerned. There is an ongoing discussion about this issue from the 1970's until today. This discussion, though, seems to be old fashioned for steady state flows. Indeed, the availability of immense computational power permits extension of domains until any distortion of the flow due to the outflow can be overcome. For unsteady (periodic) flows, the issue of appropriate boundary conditions will never be overcome, since the periodicity extends to infinity and computational domains are finite. One of the most successful concepts that is being used in the literature at outflows is the so called free boundary condition. Although it has been successfully used for periodic flows, this concept is primarily well known for steady state flows. This is due to the fact the free boundary conditions has not been used in benchmark periodic flows such as the von Karman vortex street in the flow around a circular cylinder at Re = 100 or the Poiseuille-Benard flow in a channel where traveling Bernard roll cells are created. In this work, these two benchmark flows are studied using the concept of the free boundary condition. It is shown, that the flow occurs undisturbed up to the outlfow without any distortion in the interior of the domain. In this way, the important characteristis of the flow (periodocity, calculation of grad coeeficient) are studied without any issue. Any distortion close to the outflow does not propaget upstream of the outflow. The most attractive attribute of the free boundary condition is that requires no assumption at the outflow boundary. In this way, the character of the numerical experiment is unaffected. |
Sunday, November 24, 2024 8:13AM - 8:26AM |
A14.00002: Thermomechanics of a drinking bird toy under radiative heating Shrabin Bajracharya, Varghese Mathai A drinking duck is a traditional toy based on the principles of a heat engine. It operates by wetting the bird's head, causing evaporative cooling and condensation of the liquid inside the model, which rises and shifts the center of mass of the model. This process makes the duck tip and "drink," repeating the cycle until the water source is depleted. Here we experimentally study the drinking bird's dynamics in a setting where the thermodynamic cycle is modified, specifically by replacing the evaporative cooling of the head with radiative heating of the bottom of the toy using an infrared emitter. We develop a mathematical model combining concepts from physical damped pendulums with an evolving thermo-mechanical loading. We present comparisons between experiments and model predictions and discuss the crucial parameters including ambient conditions necessary to design the toy. This work might have utility in undergraduate education, combining key concepts of mechanical oscillators with non-equilibrium phase-change thermodynamics. |
Sunday, November 24, 2024 8:26AM - 8:39AM |
A14.00003: Improving Direct Air Capture of Carbon Dioxide with Geometry-induced Instability Marc Antoni Guasch, Brendan McCluskey, Alex J Warhover, Parisa Mirbod, Roman O Grigoriev, Ari N Glezer, Michael F Schatz Many proposed systems for removing carbon dioxide directly from the atmosphere rely on wall bounded, low-Reynolds-number flows, thereby suffering from poor rates of mass transport. Incorporating geometric wall textures (grooves transverse to the flow) can give rise to flow instabilities that may improve mass transfer with low additional cost in system pumping power. In channel flow geometries, prior numerical simulations indicate that the flow becomes unstable at a critical Reynolds number of order 100; the resulting secondary flow is predicted to exhibit stable waves reminiscent of Tollmien-Schlichting modes. We report experimental measurements in a channel with one wall textured by spanwise grooves placed periodically in the streamwise direction. We examine instability onset and the resulting secondary flow as a function of the channel aspect ratio. Additionally, 2D and 3D simulations of the early transition process are presented for groove patterns with differing periodicity. |
Sunday, November 24, 2024 8:39AM - 8:52AM |
A14.00004: Evaluation of Drinkable Water Permeation through the Membrane of a Centrifugal Reverse Osmosis Module Hasib Ahmed Prince, Alperen Turkyilmaz, Mustafa Usta, Cosan Daskiran Fluid permeation in membranes is a complex process influenced by pressure gradient, solute concentration, membrane permeability, and fluid dynamics. Understanding these mechanisms is crucial for optimizing desalination systems. Two distinct approaches are widely used to evaluate the mass transport in desalination membranes: the thermodynamic equilibrium-controlled (TEC) approach and the mass transfer-controlled (MTC) approach. The TEC approach assumes that the local osmotic pressure is equal to the transmembrane pressure with infinite permeability, without taking the membrane properties into account, whereas the MTC approach considers membrane permeability and area to evaluate water recovery. In the present study, the water recovery rate and specific energy consumption of a novel centrifugal reverse osmosis (CRO) module are evaluated using both approaches for different feed flow rates. The pressure accumulation in the CRO module due to centrifugal forces is computed through computational fluid dynamics (CFD) simulations. The feed flow rate has effects only in the MTC approach. For a larger flow rate, the evaluated operating pressure of the CRO module is found higher in the MTC approach to achieve a certain water recovery rate. Both approaches show similar results at very low flow rates such as 0.01 GPM. The net specific energy consumption of CRO is 30% less than that of RO in the TEC approach for a 50% water recovery rate as reported previously, and this amount decreased to 18% for the more realistic MTC approach for a 0.1 GPM feed flow rate. |
Sunday, November 24, 2024 8:52AM - 9:05AM |
A14.00005: Numerical analysis of slip flow in a Permeable Wall Microchannel Edgar Ramos, Jose Lizardi, Federico Mendez, Ian Guillermo Monsivais Montoliu In this work, a Newtonian fluid flow circulating in a rectangular microchannel with permeable walls is investigated under slip conditions. It should be clarified that this is a purely hydrodynamic problem, therefore, the objective of this work is to obtain the pressure field and velocity profiles in the longitudinal and transverse directions. Therefore, the fluid mechanics equations to be solved in this problem are the continuity and momentum equations in the $x$ and $y$ directions, which are presented in a dimensionless form and rewritten in their variational form in order to adapt them to FreeFem++, a free software which enables to obtain the solution to partial differential equation systems, obtaining results that are presented graphically in order to make a qualitative and quantitative comparison of different conditions in the permeability and slip properties in the microchannel walls. In this way, this study attempts to make a contribution to further applications in different researching areas and projects. |
Sunday, November 24, 2024 9:05AM - 9:18AM |
A14.00006: Topology of the Counter Rotating Vortex Pairs in Parallel Jets in Crossflow Aravind Chandh, Benjamin L Emerson, Tim Lieuwen The formation and evolution of the Counter Rotating Vortex Pairs (CVP) are among the critical phenomena associated with the Jet in Crossflow (JICF) flowfield. These time-averaged vortical structures are the dominant structure in the far field of the JICF flow field. They are associated with enhanced overall mixing efficiency for the JICF flow field compared to a free jet or mixing layer. In this work, we experimentally characterize the topological changes associated with the evolution of the CVPs when the flowfield consists of 2 or 3 jets arranged in a parallel/ inline configuration. 5 kHz Stereo Particle Image Velocimetry (SPIV) measurements of the transverse plane were performed at distinct locations from the jet exit as the momentum flux ratio (J) of the jets and the spacing between the jets (L) were systematically varied. Using these measurements, we characterize the change in strength of the CVPs of the coupled jets and characterize the modifications to the flowfield induced by the coupled CVPs. This work reports the combination of J and L where different CVP topologies (merged vs distorted vs distinct) are observed. |
Sunday, November 24, 2024 9:18AM - 9:31AM |
A14.00007: Frictional resistance of turbulent pulsating air flow in a circular pipe Dnyanesh Mirikar, Prince Kaushik, Ayush Awasthi, Harekrishna Yadav An experimental investigation is carried out for turbulent pulsating air flow characteristics in a circular pipe. The velocity and pressure drop measurements are used to analyze the effect of pulsation parameters on the flow resistance. The pulsating flow is generated by acoustic excitation in a pulsation chamber. The pipe length of 2 m with 15, 20, and 25 mm diameters is used. The Reynolds number varies from 5000 to 8000, at pulsation frequencies of 5-90 Hz (Wo=10-75) and amplitudes (A) of 20-50%. The spectral analysis of pulsating flow velocity at the center of pipe's exit reveals that at Wo=43-61, the flow exhibits higher turbulence, leading to increased flow resistance. For Wo<20-30, the turbulence induced by pulsations is minimal. When Wo>61, the flow becomes more coherent, resulting in reduced flow resistance. The highest increase in time-averaged pressure drop () typically occurs between Wo = 43-61 at a given A%. When the pipe diameter is changed while maintaining same Wo, turbulence levels are highest for smaller diameters, suggesting that the turbulent structures can penetrate toward the center of the pipe. Additionally, as the pipe diameter increases, the Wo at which begins to rise relative to the steady flow arrives earlier. A smaller diameter with higher pulsation amplitude reduced flow resistance, minimizing losses. The highest increase in time-averaged pressure drop () typically occurs between Wo = 43-61 at a given A%, which could enhance heat transfer or cleaning processes. |
Sunday, November 24, 2024 9:31AM - 9:44AM |
A14.00008: Heavy-lift Multirole Agricultural Drone with Zero Carbon Emissions Roberto Sanchez This study presents the design and analysis of a hexacopter specifically engineered for agricultural applications, such as seed planting. The hexacopter is designed to lift a payload of 60 lbs to a hover height of 10 feet for a duration of 17 minutes. Detailed engineering calculations were performed to determine the necessary thrust, power, and battery capacity. The hexacopter features six T-Motor U8 Pro II motors, each delivering up to 750 W of power, paired with 15x5.5 Carbon Fiber Propellers to achieve optimal lift and efficiency. The propeller blade spacing and number of blades were designed to minimize vortex interaction, thereby enhancing aerodynamic performance and stability. The power system is supported by Tattu plus 6S 12000mAh 22.2V 15C LiPo Battery, ensuring sufficient energy supply for prolonged operations. Stress analysis confirms the robustness of the selected components under operational loads. This design demonstrates a feasible, cost-effective solution for agricultural tasks, specifically seed planting, by providing precise and efficient distribution over large areas. The proposed hexacopter design showcases significant potential for enhancing productivity and efficiency in agricultural operations. |
Sunday, November 24, 2024 9:44AM - 9:57AM |
A14.00009: High-Speed Digital Imaging in Advanced Fluidics Applications Matthew Vayner In recent years, high-speed cameras have revolutionized the visualization and analysis of complex fluid behaviors at both the micro and macro scales. For the micro scale, the ultra-fast temporal resolution of high-speed cameras enables groundbreaking discoveries in microfluidic device optimization, detailed flow visualization in microscopy and cytometry, and exceedingly accurate velocity field measurements through techniques such as particle image velocimetry (PIV). For the macro scale, Schlieren imaging and dynamical studies of magnetohydrodynamical (MHD) phenomena have emerged as increasingly popular methods of imaging invisible fluid flows and plasmas, respectively. Specifically, with MHD, high-speed imaging can capture some of the most rapid transient events including kink instabilities, magnetic reconnection, and other forms of turbulent flow (Rayleigh-Taylor, Kelvin-Helmholtz). |
Sunday, November 24, 2024 9:57AM - 10:10AM |
A14.00010: Experimental Quantification of Flow in an Impactor Liam John White, George Gianoukakis, Tomas Emilio Rojas Carvajal, German M Drazer, Edward P DeMauro In this work, the flow field inside a trap impactor is experimentally and numerically investigated using PIV, backlit imaging, and COMSOL simulations. Trap impactors are a class of impactors used to separate particles based on size and are typically used in areas such as air quality monitor, biological sample filtering, and other applications. Using an Nd:YAG double pulsed laser for PIV, the axisymmetric flow field emanating from the impactor nozzle for Reynolds numbers between 2000 and 18000 are captured between the exit plate of the nozzle and the top of the trap. Velocity profiles in the axial and radial directions are plotted demonstrating jet development downstream of the nozzle exit and return flow impacting on the exit plane. Backlit imaging is used to capture large scale flow features, driven by viscous shear and turbulence, present in the flow. |
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